Melanopic photometry

Abstract

Visual lighting effects have been seriously studied for more than 500 years. It was not until 2002 that physicians and biologists paid attention to the fact that the light that enters the human eye has non-visual, biological effects. Human Centric Lighting (HCL) examines the visual effects of light on human activity. Electric lighting plays a critical role in maintaining human health in today’s world, as most of us spend much of our time indoors. In 2002, a third type of photoreceptor was discovered – a nerve node cell in the retina (photosensitive, Retinal Ganglion Cell, pRGC). pRGC cells contain melatonin pigments (melanopsin) and are responsible for the spectral response of photosensitive cells. The maximum response of melatonin is achieved at a wavelength of approximately 480 nm. Fig. 1 also shows the response curves of L-, M-, and S-cones and rods based on their specific pigments. Using the response curves of L-, M-, and S-cones and rods, and having the spectra of light sources and the amount of light on the outer surface of the eye, it is possible to determine the spectrally weighted illuminances for five photopigments in the human eye. For research purposes, it is desirable to record the illuminance values for all five α illuminances. They indicate which of the photoreceptors is responding and where the light of the current lamp type is emitting. The manufacturers of light sources should be able to provide α-wave illuminances for their lamps. The International Commission on Illumination (CIE) suggested Exeltoolbox, which allows calculating these illuminances based on the spectral distribution of the lamp power. Cone-dominant metrics such as CCT (correlated colour temperature), illuminance, and luminance are not comprehensive, so melanopsin-based photosensitivity should be considered in specifications, guidelines, and during research.